Imogen Anthony has modelled at Fashion Week before…but never like this.

The Sydney socialite gate-crashed the Sydney Opera House forecourt on Sunday ahead of Dion Lee's opening show at Mercedes-Benz Fashion Week Australia.

The co-ordinated interruption was an unauthorised show on the MBFWA calendar with independent Australian designer Joshua Mullane launching his Psuedo collection in rogue style.

Joshua Mullane is the ex-boyfriend of Francesca Packer-Barham and the brother of Pia Miller's boyfriend Tyson Mullane.

However, he and his fashion entourage were swiftly moved along off the Opera steps by security and police.

Along with 11 other models, Imogen took part in the renegade fashion show, for which she sported a see-through thigh-skimming black dress.

The sheer metallic fabric also offered a glimpse of her statement black lingerie underneath.

Completing her outfit, the 25-year-old added black ankle boots and also carried a white faux fur on one shoulder with the brand's name inked vertically along the middle.

The girlfriend of radio shock jock Kyle Sandilands proudly posted photos and video after the event across her Instagram account.

"Today we celebrated the launch of #MBFWA in our own way by launching @joshuamullane's new #PSEUDO collection out the front of the Opera House, essentially crashing the media at a show that ended up being an hour and a half late anyway."

"Fashion is a form of expression. An art. It doesn't matter who you are or how much you have. It's about finding and expressing YOURSELF," Imogen told fans.

Speaking to Pedestrian TV about the unconventional show, Joshua said: "Obviously a fashion show is about creating hype for your brand but this was also a protest. Today was a statement about emerging artists in Australia who don't have easy access to showcase their talent.

"To get a spot at fashion is extremely expensive and lot of great talent and art is lost. It's a shame and doing this today was about disrupting that system," he added.

And it seems the group couldn't help but celebrate their little victory afterwards, with video of the starlet twerking in a leopard print jumpsuit, complete with zebra print boots, later shared on her Stories.

Imogen has dared to bare on the fashion week catwalk before, when she modelled for Bondi Bathers in 2014 and strutted her stuff in the sandkini – a swimsuit made entirely of sand.

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